Fastener setting device



May 6, 1969 E. J. SOSNOWICZ ET AL 3,442,105

FASTENER SETTING DEVICE Filed Jan. 19, 1966 Sheet of 5 EDWARD J.SOSNOWICZ FRANK M. WILLIS BY WW ATTORNEY Ma 6, 1969 J, sosmow cz ET AL3,442,105

FASTENER SETTING DEVICE Filed Jan. 19, 1966 Sheet 2 of 5 FIG. r

FIG. 4

INVENTORS EDWARD J. SOSNOWICZ FRANK M. WILLIS ATTORNEY May 6, 1969 w zET AL 3,442,105

FASTENER SETTING DEVICE Shee t Filed Jan. 19, 1966 M N I... mm my M s wM D A z 2 M E 2 i M wfi I I li a \N 2 a a s 2 2 ATTORNEY y 6, 1959 E. J.SOSNOWICZ E Al. 3,442,105

FASTENER SETTING DEVICE Filed Jan. 19, 1966 Sheet 4 of 5 I 1 is 7.7101'" II I I INVENTORS EDWARD J. SOSNOWICZ ATTORNEY May 6, 1969 E. J.SOSNOWICZ ET L FASTENER SETTING DEVICE Sheet Filed Jan. 19, 1966INVENTORS United States Patent 3,442,105 FASTENER SETTING DEVICE EdwardJ. Sosnowicz, Colwyn, Pa., and Frank M. Willis, Sewell, N.J., assignorsto E. I. du Pont de Nemours and Company, Wilmington, Del., a corporationof Delaware Filed Jan. 19, 1966, Ser. No. 521,641 Int. Cl. 1321i /00;B21d 26/08 US. Cl. 7256 11 Claims ABSTRACT OF THE DISCLOSURE A devicefor setting electrically fired explosively-actuated fasteners comprisinga current-sensitive explosive in contact with a first electrode and asecond electrode. The device comprises a supporting body for twoelectrodes one of which acts as a positioner for the device with respectto the fastener and is yieldably mounted in the body. The secondelectrode is mounted in the body for independent movement with respectto the positioning electrode in a direction parallel to the direction ofyieldable movement of the positioning electrode.

head portion and a shank portion having a central longitudinal recess.The recess holds an explosive charge which conventionally is one capableof ignition merely by the application of heat. In use, the shank of thefastener is pressed through aligned holes in two panels which are to bejoined, with the explosive charge located in the portion of the shankpositioned slightly beyond the far surface of the metal plate mostremoved from the head of the fastener. When the explosive charge isactuated, i.e., detonated or deflagrated, the walls of the fastener inthe vicinity of the charge are bulged out and the fastener thereby holdsthe metal plates tightly together.

While various methods have been suggested to fire the explosive chargein the fastener, viz, percussion, safety fuse, or high voltage staticdischarge, by far the most commonly used method is by means of anelectric heating device which is applied to the fastener head and, bythermal conductance, raises the temperature of at least the head of therivet until the ignition temperature of the explosive charge isattained. The necessity for the use of a cumbersome-heat-producing toolin such work is a distinct disadvantage and results in increased laborcosts or, where the space surrounding the head of the fasteners isrestricted, often precludes their use. The presently used tools areheavy, require a bulky power source trailing behind the operator, buildup considerable heat in use, adding to the operators frustrations, andrequire a high degree of adjustment and maintenance of the heating tip.Further, considerable pressure must be applied in using the conventionalheating tools.

An explosive fastener now has been developed which does not depend uponheat transfer through the head for actuation of the explosive charge,but rather employs a charge which is actuated in microseconds by lowelectric current passing therethrough. These new fasteners, which can berivets, bolts, screws, nails, pins, or the like, are described morethoroughly in copending application Ser. No. 393,550, by W. E. Schulz,filed Sept. 1, 1964,

Patented May 6, 1969 which was abandoned in favor of continuationdn-partapplication SJN. 521,599, filed Jan. 19, 1966, and now US. 3,332,311,issued July 25, 1967, which is incorporated herein by reference. Theexpanding explosive charge therein comprises a detonating explosivecompo sition such as, typically, lead azide in intimate admixture withparticles of an electrically conductive, semiconductive, orvoltage-sensitive material, preferably carbon and typically graphite inadmixtures with amorphous carbon. The fastener is provided with anopening, preferably through its head, into the recess containing theexplosive charge, and an electrode, which is insulated along its entirelength but has bare ends, is inserted into the recess. A portion of theelectrode within the recess is contoured, e.g., headed, to precludeforceful eject-ion of the conductor upon actuation of the explosivecharge. The surface of the electrode within the recess is peripherallycoextensive with the walls of the recess. The conductive,semiconductive, or voltage-sensitive particles dispersed in theexplosive charge are believed to provide a plurality of conducting paths(bridges) of microscopic cross-section but measurable resistancepreferably of, e.-g., 1 to 1000 ohms, between the electrode and the bodyof the fastener. The passage of an electric current supplied by a (1 tomicrofarads) capacitor charged by a (nominal 30 to volts) direct currentsource is sufficient to effect actuation of the explosive charge andexpansion of the walls of the shank of the fastener within microseconds,at rates many times faster than that required to fire conventional heatactuated fasteners. However, there still remains a need for alightweight, nonhazardous tool to set, i.e., bring about actuation of,the explosive charge of the recently developed fasteners and, in someembodiments, to eliminate any protrusion of the electrode above thefastener head after firing.

In accordance with this invention, there is now provided a device forsetting the aforementioned electrically fired, explosively actuatedfasteners, which is characterized by its simplicity, compactness,reliability, and rapidity of setting.

The devices of this invention for setting the aforementionedelectrically-fired, explosively-actuated fasteners comprise:

(a) positioning means which is yieldably mounted for movement parallelto the axis of said fasteners during setting and which engages the bodyof the fasteners and forces them into the workpiece,

(b) a conductive electrode independently movable with respect to (a) ina direction parallel to the direction of yieldable movement thereof toengage an electrode in said fasteners, and

(c) a power source which is connected to electrode (b) and thus to oneelectrode, usually a central electrode, of the fasteners.

The positioning means is preferably tubular, of metal or otherconductive material and substantially coaxial with electrode (b).Preferably, the positioning means is in the portion of the devicecircuit connected to one pole of the power source, usually through thebody of the device, and engages the body electrode of the fasteners.Alternately, however, the positioning means can be non-conductiveplastic or other insulating material, the fastener bodies being merelygrounded, e.g., on the workpiece together with the device body. Thepositioning means also provides the force necessary to draw parts of theworkpiece together, e.g., in the blind fastening of panels.

After the positioning means in devices of this invention is brought intocontact with a fastener and the body thereof is pushed farther towardthe workpiece, electrode (b) is brought into contact with the fastenerscompleting the circuit therethrough, actuating the explosive therein andsetting the fasteners. During this forward body movement, pressureapplied by the positioning means on the fastener and workpieceincreases. This force on the fastener and workpiece is preferablyapplied by a spring, preferably a coil spring, abutting the positioningmeans, i.e., either the electrode per se or an appurtenance thereto, andalso abutting some stationary element in this body of the device.Alternately, for example, the force applied to the positioning meansurging it toward the workpiece can be supplied by having the rearwardportion of the positioning means-tubular electrode act as a piston in anair cylinder or by applying some other yieldable force against thepositioning means in the direction of the workpiece, e.g., by placing ayieldable elastomeric cushion abutting the rear of the positioning meansand the device body.

In a preferred embodiment of the invention fasteners are suppliedatuomatically in front of the electrodes by a pneumatically drivenfeeding head mounted and axially movable along the nosepiece bearing thepositioning means-tubular electrode. In one preferred embodiment, thisfeeding head is actuated to supply each fastener by the current whichsets the preceding fastener. Alternately, however, a separate switch,e.g., a switch in the pistol grip handle, can be used to actuate thefeeding of each fastener to the feeding head. In one other embodiment ofthe invention particularly useful with fasteners having centralelectrodes with protruding heads, the devices contains a means fordriving the electrode (b) forward rapidly to peen the head of thefasteners.

The power source is preferably of the capacitive type usually of 1 to100 microfarad capacity and preferably with a battery recharger coupledtherewith. Alternately, the firing current or the recharging current canbe supplied directly from any conventional D.C. or rectified A.C.source. In order to lengthen the life of the batteries in the manualdevice and control charging time of the capacitor, preferably aresistance, usually of 8000 to 20,000 ohms, is connected in series withthe power source, preferably on the probe (electrode (b)) side.

The conductive elements of the devices of this invention can be ofbrass, bronze, steel, aluminum or other metals including any of theconductive materials commonly used in hand tools. For non-conductiveelements, plastics including nylon, polytetrafluoroethylene,polyethylene, polypropylene, acetal resins, the phenolic and aminoplastthermosets, as well as laminates thereof can be used.

-In the accompanying drawings which illustrate the invention:

FIGURE 1 is a schematic, cross-sectional view of an electrically fired,explosively actuated fastener being fired by a device of this invention,

FIGURE 2 is a cross-sectional view of the manual device of thisinvention, the parts therein being shown in the at rest position,

FIGURE 3 is a cross-sectional view of a finger-manipulated device inaccordance with this invention,

FIGURE 4 is a schematic diagram of the basic electric circuitry involvedin the devices of this invention,

FIGURES 5 and 6 are cross-sectional elevational and partial top views,respectively, of an automatically fed device of this invention.

FIGURE 7 is a schematic diagram of electric circuitry which can beemployed in accordance with this invention to correlate feeding offasteners with setting of a preceding fastener.

FIGURES 8 and 9 are views of a device of this invention adapted to setfasteners and instantaneously thereafter to peen any portion of theelectrode protruding above the fastener head flush therewith.

In FIGURE 1, an electrically fired rivet having a body 1 of aluminum,bronze, brass or other conventional fastener metal is positioned alreadyfor setting in aligned holes in parts 2 and 3 to be joined. Body 1 has arecess passing axially through the head and shank thereof. At the upperpart of this recess is an electrode 4, usually of metal similar to body1, bare at its upper and lower ends but insulated from body 1 by aninsulating layer 5, e.g., a. coating of Formvar polyvinyl-methylalresin. Within the aforementioned recess adjacent the inner end ofelectrode 4 is an electrically fired explosive charge 6, e.g., of, byweight, 65% of 25p. dextrinated lead azide, 16% of 2-l0a micronizedgraphite, 4% nitrostarch, 13% tetracene and 2%-29p. oil furnace blackpin set at 35,000 p.s.i. The bottom of the recess in body 1 is closedwith a rubber spacer 7 and soft carbon steel plug 8. After charge 6 isdetonated as will be presently described, the shank of body 1 expands tothe position shown by the dotted lines 9.

The device of this invention shown in FIGURE 1 comprises annular metalelectrode 10 which engages the head portion of the body 1 of the rivetand central metal electrode 11 which engages electrode 4 in the rivet.Annular electrode 10 is positioned to engage the rivet first and thenplastic or other insulating base 12 is depressed to move electrode 11into engagement with electrode 4 of the rivet. Electrode 10 is held inengagement with the rivet by spring 13 as electrode 1 lis moved intoengagement. When both electrodes 10 and 11 have engaged the fastener,current from a power source comprising battery 14 and capacitor 15passes through the electrodes and explosive charge 6 as shown by thearrows in FIGURE 1, detonating charge 6 and setting the rivet.

In FIGURE 2, a tool, i.e., a gun, is shown which has a tubular,barrel-like body which is of an electrically conductive material,typically a metal, having a hollow barrel 20 and a hollow handle 21. Anosepiece 22, also of a conductive material and having a centralaperture therethrough is mounted for reciprocal forward and backwardmovement in the muzzle of the gun barrel parallel to the longitudinalaxis of the barrel. Nosepiece 22 forms one electrode in the device ofthis invention. Spring 23, which is mounted on stationary dielectricspacer and guide 24 near the rear of the barrel, extends substantiallythe length of the barrel into contact with the rearward surface ofnosepiece 22, restricting its rearward motion. The forward portion ofdielectric spacer and guide 24 forms a cylindrical chamber portion 25.The extremity of the chamber portion toward the muzzle is abutted byelectrode 26 which is mounted along the longitudinal axis of the barrel,the forward portion of the electrode 26 extending into and being axiallyaligned with the aperture 27 in nosepiece 22. The diameter of electrode26 is slightly less than the diameter of the aperture to allow itssmooth passage through aperture 27 during reciprocal movement ofnosepiece 22, relative to the barrel. Spring 28, which is mounted oninsulator guide 29 and extends into the rear of cylindrical chamberportion 25, biases the contact means forward and acts as a cushion toprevent overtravel of and damage to electrode 26. Electrode 26 isinsulated from nosepiece electrode 22 by dielectric sleeve 30, which isin close peripheral contact with the cylindrical surfaces of bothcomponents.

The electrical components of the gun, i.e., device or tool, convenientlyare contained in the cavity in the handle 21 of the gun. Thesecomponents make up the energy package, i.e., power source, whichcomprises, basically, capacitor 31, which usually is of about from 1 tomicrofarad capacitance, preferably about 10 to 20 microfarads, andpreferably has positive and negative terminals as designated in thedrawing, charged by a negative 30 to volt DC. power source 32, i.e., abat tery or batteries. Resistor 33 (connected between the negative sideof the battery 32 and negative side of capacitor 32 of about from 8000to 20,0009 resistance prevents a current flow in excess of the batterymanufacturers recommendation. Lead 34 from the negative side ofcapacitor 31 is connected to mount 29 and is in electrical contact withspring 28 which is, in turn, in electrical contact with electrode 26.Thus, electrode 26 is connected electrically in circuit with capacitor31. Nosepiece electrode 22 is connected to the positive side ofcapacitor 31 through barrel and housing 20 and lug 35- in the hollowhandle of the gun body. Jack 39 provided in the handle of the gun forattachment of the hand device hereinafter described is connected to thenegative side of the capacitor.

To set one of the electrically fired, explosively actuated fasteners 36,i.e., to actuate (detonate or deflagrate) the explosive charge 37therein, the gun is applied to the head of the fastener with aperture 27substantially centered over the insulated electrode 38 in the fastenerhead. With the gun in position and capacitor 31 charged, the operatorpushes the gun against the head of the fastener 36 and toward thesurface of the parts to be joined by the fastener, thereby exertingpush-down force on the parts. Contact of nosepiece 22 with the head ofthe fastener 36 connects, electrically, the fastener body to thepositive side of the capacitor 31. As push down force is exerted,nosepiece 22 moves back into the muzzle of the barrel against theresistance presented by spring 23. The compression force (resistance) ofspring 23 is selected and/or adjusted to regulate the total push downexerted to move nosepiece 22 back into the muzzle of the barrel and tobring electrode 26 into electrical contact with the electrode 38 in thehead of the fastener 36. As the nosepiece electrode 22 moves back intothe muzzle 20 the forward tip of electrode 26 protrudes through theinsulating guide 30 in the nosepiece to contact the electrode 38.Contact of electrode 26 with the electrode of the fastener places theelectrode 38, which becomes connected to the negative side of thecapacitor 31 and the conductive particles in the explosive charge 37, inthe electric circuit described above. The energy in the capacitor 31 isdischarged through spring 28, chamber 25, and electrode 26 to electrode38, from electrode 38 through microscopic bridges provided by conductiveparticles in the explosive composition 37 to the body of the fastener 36which is connected in the electric circuit, i.e., to the positive sideof capacitor 31, through nosepiece electrode 22, housing 20 and lug 35,as described above. The explosive composition is actuated, e.g., isdetonated or deflagrates, in microseconds, typically 1 to 15 0microseconds, after contact is made. Actuation of the explosivecomposition, as detected by a click, radially expands the fastener bodywithout rupturing it. When the gun is removed from the panels, thecompression force in spring 23 is released and nosepiece electrode 22 ispushed forward in the muzzle by the spring 28. The gun can be made tofit in the operators hand in a position designed for minimum fatigue andmanipulated by body and shoulder motion, minimizing wrist action. Jack39 can be used to connect the power source of the gun to a hand deviceof this invention, e.g., of the type shown in FIGURE 3, by a coaxialcable.

As shown in FIGURE 3, devices of this invention can be made small enoughto fit in a thimble-like holder which can be slipped onto the tip of anoperators finger and particularly adapted for use in locations wherethere is small clearance. In this embodiment, housing 41 is a tubularmetal body and nosepiece 42 is mounted for movement along thelongitudinal axis of the housing against the resistance presented byspring 43 which biasses it forward. Electrode 44 is, in this embodiment,stationarily mounted in the housing and insulated by dielectric sleeve45.

A small coaxial cable, such as RG 178B/U (military designation number)extends into the opposite extremity of housing 41. The center conductor47 of the cable, which is protected and insulated by the coaxial cabledielectric 48, is attached to a washer-like piece 51, typically ofbrass, which is insulated from body 41 by a machined piece 50 of a harddielectric such as a polyoxymethylene (Delrin) or nylon. The conductivewasher-like piece 51 is in physical contact with electrode 44. Thebraided shield 52 of the coaxial cable is attached to the washer-likepiece 49. The assembly is held in place in housing 41 typically by asnap-ring 53 and provides a means of electrically connecting the body ofthe finger tool in circuit with the power source, e.g., those of FIGURESl and 2. Conveniently, a power source comprising the batteries, acapacitor, and a current limiting resistor can be stored in theoperators pocket or afiixed to a holster by a clip.

Operation of the finger-tool is basically the same as that of thedevices of FIGURES 1 and .2. In the operation of this tool, theoperators finger action serves to cushion electrode 44 and to precludeits overtravel when contact is made with the head of the fastener in asimilar way to the action of springs 13 and 23 in FIGURES 1 and 2,respectively.

The electric circuitry employed to actuate the conductive explosivecomposition within the fastener can be seen more readily by reference toFIGURE 4. In this figure, the designation of electric components is asdescribed above for FIGURE 2. To repeat somewhat the discussion ofFIGURE 1, in the operation of the gun, the capacitor 31 is charged tobattery voltage through resistor 33. When the electrode 26, which isconnected in the electric circuit directly as in FIGURE 3, or through aspring as in FIG- URES 2 and 5, is in contact with the electrode of thefastener, the capacitor is discharged through electrode 26, theconductive explosive mixture within the fastener, the fastener body, andthe body of the gun. The resistance value for resistor 33 is selected tolimit the current from the power source 21 to preselected value, e.g., 5to 10 milliamperes, which regulates the recharge time for capacitor 31.

FIGURES 5 and 6 show a gun adapted to receive fasteners automaticallyand pneumatically fed to it and to aid in positioning the fasteners inaligned holes in panels to be joined. The nosepiece 60 shown in thesefigures replaces the nosepiece 22 of the manual gun shown in FIGURE 2.The increased length of the nosepiece 60 over that of the nosepiece 22of FIGURE 2 is required to accommodate the Y-feeding head 61 of thepneumatic feeding and positioning mechanism. The nosepiece 60 has a lip62 providing a piston for operation in cavity 63. Electrode 76, which ismovable in nosepiece 60 in a similar manner to its motion in nosepiece22 in the manual gun, is lengthened to correspond to the increasedlength of the nosepiece 60.

The body of assembly 61 fits about the nosepiece 60 and peripherallyengages lip 62. Cavity 63 is coaxial with nosepiece 60 and with thebarrel of the gun. Tubular passage 64 which intersects passage 65 withan included angle, e.g., of 20 to 40, being formed between thelongitudinal axes of passage 64 and the exit passage 65 in assembly 61leading from cavity 63, an enlarged rear portion of passage 65. Cavity63 defines an air cylinder within which lip 62 acts as a piston. Tap 72is provided to connect the air cylinder with an external source ofcompressed air.

The snout 67 on assembly 61 is of frustro-conical configurationcontinuing, and being coaxial with, passage 65. The snout provides anaperture 68 whose diameter is slightly larger than the shank of thefastener with which the gun is to be used but less than the headthereof. The frustro-conical snout is bisected (split) longitudinallyand the two portions thus formed mounted on body 61 and held closed byfiat springs 69. These springs permit halves of snout 67 to spread andmove apart radially providing sutficient clearance for the head of thefastener to pass through aperture 68. The wall thickness of the snoutdiminishes from a maximum at the section mounted adjacent body 61 to aminimum at the aperture. The interior of the snout is highly polishedand the edges rounded slightly to provide a smooth surface which willbuild up minimal friction during passage of the fastener.

The feeding head 61 is shown in FIGURES 5 and 6 slidably mounted onnosepiece electrode 60 by a pair of springs 70 which can extend from themuzzle of the barrel to the feeding head. The springs are bent aroundpedestals which prevents the springs from becoming straight. The springsexert neither a push or pull-force but act to insure return of thenosepiece attachment to its at rest rearward position during actuationof the gun.

FIGURE shows a fasener 73 being fed into section 65 of the attachmentthrough the bore of section 64. Pressure applied to air cylinder 63through tap 72 displaces the head 61, forcing it forward with respect tothe nosepiece 60 so that the path between section 64 and the interior ofsnout 67 is unobstructed.

The dotted lines in FIGURE 5 show the lip 62, electrode tip of nosepiece60, and the fastener 73 in the sno t 67 in position to be inserted inparts to be joined. After the initial pulse of air is exerted, airpressure is vented from the air cylinder 63 primarily by leakage of airaround lip 62, allowing the head 61 to move back toward the handle ofthe gun. The time between the pulsing of air that blows a fastener tothe head 61 and the time the air vents overlaps. The pulse of air andair pressure in the head assembly and the force of springs 69 trap andhold the fastener in place in the nose of the attachment until contactis made between the head of the fastener 73 and the tip of nosepieceelectrode 60 in functioning of the gun, no matter what the position ofthe gun might be, i.e., there is little or no dependence on gravity ,orpawls (dogs). The two portions of the snout are held together by theforce of springs 69, trapping the head of the fastener.

In FIGURE 6 snout 67 and the tip of nosepiece electrode 60 are shown inposition to set the fastener 73. The snout 67 and fastener 73 are in theposition shown by dotted lines in FIGURE 5. At the time the shank of thefastener is inserted into aligned holes in the parts. As increasedpushdown force is exerted, the two portions of the snout spread apart tofree the head of the fastener and the head attachment moves back towardthe barrel of the gun permitting the tip of nosepiece electrode 60 topush the fastener 73 all the way into the holes in the parts as shown inFIGURE 6. With the application of still greater pushing force, thenosepiece 60 itself moves rearward in body 75 against the force ofspring 74, thereby causing electrode 76 to come forward with respect tonosepiece 60 and to protrude through the aperture in the snout, makingelectrical contact with the electrode of the fastener 73.

The power source comprising capacitor 80 and resistor 81 is groundedthrough lug 83 to body 75 and electrodenosepiece 60 while the negativeterminal of the power source is connected to electrode 76 through spring77 in dielectric housing 78 abutted against stationary abutment 79. Allof the aforementioned elements function like the corresponding elementsin FIGURE 2. Resistor 81 and the positive side of capacitor 80 areconnected to the central circuitry of FIGURE 7 described hereafterthrough a BNC connector 84 at the base of the hollow handle of the gun.Batteries are not provided in the handle of this gun since rectifiedA.C. current from the circuitry of FIGURE 7 is the power source.

Alternatively, the adaptor for receiving and holding the fastenerssupplied from a hopper can be one which 'has means providing a firstbarrier to obstruct passage through its snout of a fastener and secondbarrier means upstream of the first barrier to obstruct movement of thefastener away from the snout, the first barrier yieldable by themovement of the probe to free the obstructed fastener.

The fasteners are conveyed to the automatic gun pneumatically from ahopper by a combined pneumatic-electric mechanism whose functioning canbe correlated with firing of the fastener and the positioning anddischarging of a fastener in the muzzle of the gun.

An example of a suitable device for supplying fasteners t0 the feedinghead 61 of device of this invention is shown in U.S. Patent 3,026,000(see particularly FIGURE 1) which is incorporated herein by reference.Other feeding mechanisms which could be used to provide fasteners to thepassage 64 in the feeding head 61 are shown in U.S. Patents 2,304,572,2,534,140, 2,706,504, 2,886,076, and 2,886,077 which are incorporatedherein by reference.

The timing of the release mechanism and feeding of a fastener to thehead 61 assembly of the gun in FIGURE 5 can be correlated with settingof a fastener by the gun in accordance with this invention through theelectric circuitry shown in FIGURE 7 in which the elements are as shownbelow. Typical ratings of these elements for a firing circuit are asshown in parentheses.

-single throw single pole toggle switch 101 and 113rectifier (type1N2071) 102-resistor (18000 at 2 watts) 103-resis.or (10,0000 at 1 watt)104-potentiometer (10,0000 at /2 watt) 105-variable resistor (25000, /2watt) 106fixed resistor (5600, /1 watt) 107current-sensitive relay (0.53milliamps) 108medium power relay (16000, volts A.C.)

109-se1f-timing air solenoidregulates flow of air to escape mechanism110solenoid air valve (l0-watts)-regulates flow of air to nosepiece111capacitor (10 fd., 150 volts D.C.)

112fuse amp) 114-capacitor (40 ,ufd., 150 volts, D.C., electrolytic) Inoperation, switch 100 is closed so that volts AC. is applied to operatethe hopper of the mechanism feeding fasteners to the gun of FIGURE 5 andcurrent is applied to contacts b of relays 107 and 108 and to thecathode side of diode 101. Diode 101 rectifies the 120 volts A.C.current through voltage-divider resistors 102 and 103 to provide anegative (90 volts) DC. power source for the capacitor discharge circuitin the gun.

When capacitor 80 in the gun is discharged by the firing of theexplosive charge in a fastener or by actuating a test switch (not shown)in the gun, the current needed to recharge capacitor 80 flowing from thevoltage divider through relay 107 and resistors 104 and 81 actuatesrelay 102. Resistor 81 limits the maximum current in the system, e.g.,to approximately 68 mililamperes, and resistor 104 controls the lengthof time that the relay 102 remains actuated by providing a shunt path ofvariable resistance, variations therein resulting in raising or loweringof the current threshold for actuation and drop-out of relay 102.Capacitor 111 smooths out the (60 cycle) ripple in the circuit andprecludes chattering in relay 111.

Since relay 111 has a light power contact rating, medium power relay 108is used to perate air solenoids 109 and 110 and is timed by relay 102.The timing of air solenoid 110, which delivers air through tap 72 toextend the feeding head and to open the fastener path therein, isregulated (timed) by relay 108. Air solenoid 109, which regulates thepulsing of air to the mechanism feeding the fasteners 73 is self timingbut requires a short pulse of 120 volts AC. to start its cycle. It ispossible to omit air solenoid A5 in some embodiments; if such is thecase, resistors 105 and 106, rectifier 113, and capacitor 114 make up adelay circuit which controls the actuation of relay 108. Resistors 105and 106 control the charging rate of capacitor 114 which regulates theactuation time of relay 108, the magnitude of delay increasing withincreasing resistance.

Actuation of air solenoid valve 110 admits compressed air into thepressure tap 72 of the gun to open the passage for the fastener in theattachment as shown in FIGURE 5. Actuation of air solenoid 109 admitscompressed air into the feeder mechanism (not shown) and conveys afastener through flexible tubing (not shown) and passage 64 into thehead 61 of the gun.

By the time that the fastener is in the snout 67 of the attachment,compressed air is sufficiently vented from the air cylinder 63 and thepositioning of the end of nosepiece electrode 60 with respect to thehead 61 becomes that shown by the dotted lines. The operator manipulatesthe gun so that the shank of the fastener is inserted and positioned inthe aligned holes in panels to be joined and presses the gun toward thepanels as described above. In response of this pressure, the sections ofsnout 67 spread apart allowing the head of the fastener to pass throughthe snout and contact is made with the end of nosepiece 60, as describedabove and as shown in FIGURE 6. Contact of electrode 76 with theelectrode of the fastener and subsequent setting of the fastener act asa switch in the electric circuit, triggering the feeding (escape orrelease) of a subsequent fastener.

As stated, firm contact of the electrode of the tool (gun) with theelectrode of the fastener is sufficient to set the fastener wihin about150 microseconds. The gun, as described, can be used to set fasteners inwhich the electrode is substantially flush with the head of the fasteneror recessed in a chamfered section of the fastener as long as there issuflicient clearance in the chamfered section to allow the electrode tocontact the uninsulated (bared) end of the electrode of the fastener.However, the gun can be modified as described below to not only set thefastener, i.e., by connecting the fastener body and conductive charge inelectric circuit with the charged capacitor, upon contact of theelectrode of the tool with the electrode of the fastener, but toinstantaneously peen any portion of the electrode which may protrudeabove the head of the fastener flush with the head.

In FIGURES 8 and 9, an embodiment of the device of this invention isshown which is adapted to set a fastener and instantaneously thereafterto peen the head and any electrode protruding therefrom. This gun alsohas a barrel-like body 120 which may be of an electrically conductivematerial, e.g., a metal. Nosepiece electrode 121 of a conductivematerial is mounted for movement in the muzzle of the body 120 parallelto the longitudinal axis of the barrel against the resistance of tensionspring 122. Contact striker head 123 rides in chamber 124 and electrode125, in the chamber portion forwardly therefrom, is mounted in thebarrel for movement along the guns longitudinal axis. The extent ofrearward movement of contact-striker head 123 and electrode '125 isrestricted and controlled by spring 126 mounted on stationary springsupport 127 which is mounted in bushing 128 near the breech of thebarrel, the spring extending substantially the entire length of thebarrel portion of the gun body. The forwward portion of spring 126extends into the cylindrical chamber portion 119 and urges striker head123 toward the workpiece. Movement of electrode 125 within the nosepiece121 during relative movement of the two is regulated by insulated guide129, which is movable in the nosepiece against the resistance of spring130. Striker head 123 is separated from the nosepiece 121 by aninsulating sleeve 131 which is in close peripheral contact with thesurface of both components. The rear of sleeve 131 engages latchretainer 132.

As may be seen in FIGURE 9, latch 133, having a central aperture whichis of larger inner diameter than the outer diameter of striker 123 isheld in groove 134, which extends circumferentially about striker 123with its rearward surface in contact with the forward surface of thelatch retainer 132. Insulating cam 135 and insulating guide 136 areprovided in the walls of the gun barrel as means of regulating movementof the latch 133 as the nosepiece 121 is moved toward the rear of thebarrel. Guide 136 has an insulated leaf spring 137 designed to providepositive return of the latch 133 to groove 134 as the striker mechanismmoves forward to fire the fastener. Cam 135 is an inclined plane, i.e.,a wedge, which is designed to move the latch 133 on an axisperpendicular to its forward travel. Compression spring 122, referred toearlier, opposes the rearward movement of the nosepiece 121, strikerhead 123 and the latch 133.

The electrical components of the tool, which are basically thosedescribed for the gun of FIGURE 2, again conveniently are contained in acavity in the handle of the gun. However the circuitry is modified toinclude, as a circuit checking means, a neon pilot light.

Neon pilot light 145 (FIGURE 8), which is an electric circuit with avoltage dropping resistor 147 (preferably of 68,000 ohms when the powersource is a 90-volt battery), with a push button switch having normallyopen contacts for momentary action, and with a current limiting resistor138 (nominally of 200 ohms when the power source is a 90-volt batteryfor protection of the push button switch contacts), provides a means oftesting the batteries 139, under load conditions. When the pushbuttonswitch 140 is actuated, capacitor 141 discharges through resistor 138and switch 140 and appears as a near short circuit simulating rivetfiring conditions and causing nearly maximum current to flow throughresistor 142. Substantially full battery voltage (nominally 90 volts) isthus impressed across resistor 142, causing the neon indicator to beilluminated. Thus, the operator can be assured that suflicient power isavailable to charge capacitor 141 in a selected time, e.g., desirably,/2 to second, to the voltage required to fire the explosive mixture inthe fastener. If the neon pilot light is not illuminated, insuflicientpower is available to charge the capacitor 141, and the power sourceshould be replaced or recharged.

To fire (actuate) the explosive charge in the recently developedfasteners with this gun and instantaneously peen the set fastener, thegun is applied to the fastener with the opening in the insulating guide129 substantially centered on the electrode of the fastener. With thegun in position and the capacitor charged, the operator presses the gunagainst the surface of the parts to be joined. As the pushing force isexerted, the insulated guide 129 moves back into electrode nosepiece121, permitting the nosepiece 121 to make contact with the head of thefastener, and the nosepiece 121 itself moves rearwardly into the barrel,thereby moving back latch 133, latch retainer 132, and striker head 123.The nosepiece 121, latch retainer 132, latch 133, and the striker head123 move toward the rear of the barrel against the combined resistanceof spring 122 and spring 126. The tension (resistance) in each of thesprings is preset and adjusted to regulate the amount of energy storedin striker spring 126 and the total force exerted by both springs iscombined to provide the resistive effort or force required to bring thestriker 123 into contact with the electrode of the fastener (this forceis resisted by the structural strength of the parts to be joined).Spring 122 will be strong enough to return the nosepiece to the forwardposition and to maintain good contact with the parts and fastener headeven after latch 133 trips and the energy (force) for spring 126 isreleased. The force, and, accordingly, the size of spring 126 isdetermined by the energy required to peen the fastener head byfiat-faced electrode 125. The force and, accordingly, the size of spring122 will be determined by the minimum requirements mentioned, i.e., thepush-down force desired to be exerted on the panels and firmly to seatthe fastener in the hole.

As the nosepiece 121, striker head 123 and latch 133 move back, latch133 is urged in a direction perpendicular to its rearward travel and tothe axis of the striker head 123 by cam 135. Latch 133 moves upwardalong the inclined plane of cam 135, becoming displaced with respect tothe groove 134 until, at a release point near the apex of cam 135, thelatch 133 is released from the groove, thus releasing the striker head123. The tension in spring 126 then is released, and the strikermechanism moves forward with respect to the nosepiece 121. Since latch133 has a central aperture larger than the maximum outer diameter ofstriker head 123, the striker head 123 can pass through the latch 133without being reengaged. As the tension in spring 126 is released, thestriker head 123 :moves forward, so that the forward surface ofelectrode fixed thereto protrudes through 1 1 insulated guide 129 tocontact the electrode of the fast-ener. Contact of the electrode 125with the electrode of the fastener incorporates the electrode and theconductive particles in the explosive charge in the electric circuit.

After firing the explosive charge, electrode 125 travels the distancecorresponding to the length of electrode or other part to be peenedprotruding above the fastener head within about 100 microseconds, thuspeening the electrode flush with the fastener head. During forwardtravel of the striker head 123, the tension of spring 122 insurescontact of the head of the fastener and the nosepiece 121 and with theparts to be joined. A delay in the peening action may be provided byplacing a spring 143 within the nosepiece axially aligned with electrode125 and referenced against striker head 123.

When the gun is removed from the parts to be joined, the tension inspring 122 is released and nosepiece 121 and latch 133 are pushedforward. As the elements move forward, guide 136 and spring 137 assurethat the latch is returned to groove 134 and the gun is readied foranother cycle. Spring 130 in nosepiece 121 pushes the insulated guide129 forward.

We claim:

1. A device for setting electrically-fired explosivelyactuatedfasteners, said fasteners comprising a currentsensitive explosive incontact with a first electrode and a second electrode that is insulatedfrom said first electrode, said device comprising a body,

(a) positioning means for engagement with said fasteners and yieldablymounted in said body for reciprocal movement therein parallel to theaxis of the fasteners during setting,

(b) an electrode independently movable with respect to said means (a) ina direction parallel to the direction of yieldable movement thereof, forengagement with said first electrode of said fasteners, and

(c) a power source connected through said electrode (b).

2. A device of claim 1 wherein said means (a) is a conductive tubularelectrode substantially coaxial with said electrode (b), said powersource (c) being connected to said electrode (b) and said tubularelectrode.

3. A device of claim 2 wherein said tubular electrode is held inengagement against said fastener by a spring which exerts a force onsaid tubular electrode in an axial direction toward the fastener as saidelectrode (b) is brought into contact with the insulated electrode inthe fastener.

4. A device of claim 3 wherein said power source cornprises at least onebattery and a capacitor connected in parallel.

5. A device of claim 4 wherein at least one resistor is hooked in serieswith said capacitor to limit the charging rate of said capacitor.

6. A device of claim 3 wherein said electrode (b) is spring loaded tolimit the maximum force which can be exerted by the tip thereof in aforward direction.

7. A device of claim 3 comprising a nosepiece includ ing the tubularelectrode, said tubular electrode being urged forward by a coil springcoaxial with said tubular electrode and abutting a stationary abutmentwithin said body, said electrode (b) being opposed in its rearwardmovement relative to said body by a second coil spring within said firstmentioned coil spring, said electrode (b) being substantially coaxialwith, insulated from and axially movable within said tubular electrodeand having its forward tip disposed rearward of the forward tip of saidtubular electrode when said device is in the at-rest condition.

8. A device of claim 7 wherein said tubular electrode is connected tothe positive terminal of said power source through said body, and saidelectrode (b) is connected to the negative terminal of said powersource, said power source being housed within said body and comprising acapacitor and at least one current limiting resistor connected inparallel with at least one battery.

9. A device of claim 7 bearing a feeding head mounted on said nosepiececomprising said tubular electrode, said feeding head having an axialpassage through which said tubular electrode and electrode (b) pass whensaid device is abutted against a workpiece and said body of said deviceis moved forwardly, and a passage which intersects said axial passagenear its forward terminus through which fasteners can be pneumaticallyfed, and means to feed air to an enlarged portion of said axial passagein front of a piston-like enlargement of said nosepiece slideablymounted within said enlarged portion to thereby withdraw said electrodesrearward and clear said intersection for feeding of another fastener.

10. A device of claim 9 additionally comprising means for automaticallyfeeding each fastener in response to the setting of the next precedingfastener which comprises a relay responsive to passage of currentthrough said electrodes, said relay activating said air fed to saidenlarged portion of said axial passage and to a fastener feedingmechanism on passage of said current.

11. A device of claim 7 additionally comprising means for simultaneouslycontacting said first electrode of said fasteners and peening the headthereof which comprises latching means which compresses said second coilspring as said body is moved forward with respect to said electrodes andmeans to release said latching means when said body and electrodes havereached a given position with respect to each other to thereby releasesaid second coil spring and drive said electrode (b) rapidly andforceably against the head of said fasteners.

References Cited UNITED STATES PATENTS 2,080,220 5/1937 Butter et a1.-37 2,387,742 10/ 1945 Burrows. 2,534,140 12/1950 Moore. 2,706,5044/1955 Moore. 2,886,076 5/ 1959 Shinkle et al. 2,886,077 5 1959 Raffertyet al. 3,166,971 1/ 1965 Stoecker.

FOREIGN PATENTS 467,514 6/ 1937 Great Britain.

RICHARD J. HERBST, Primary Examiner.

US. Cl. X.R. 29421

